There must have been a Mass. It was just so long ago, that I have forgotten. sorry to say, but the homilies and the choir were so outstanding that I’ve forgotten whether there was a Mass. It was held in a Catholic Church and the Priests presiding were Catholic, but the Lutherans fully participated.
Certainly you can have the Eucharist without the Mass, if the bread has been consecrated before (and yes, it was regular wafers). Eucharistic ministers bring the Eucharist to shut-ins all the time without the Mass. The bread was consecrated at a regular Mass and then is taken out by designated ministers, or relatives, to deliver to the shut in. My husband brought me the Eucharist when I was recuperating from my knee replacement surgery.
Sure, you can have previously confected Eucharist. If that was the case, the service you described is still abominable and a sacrilege.